When you bring the app up click on the ContentPanel to give it focus and press the down arrow. You will see the entire panel shift (this is covered by EXTGWT-2393) instead of the content panel scrolling down. If you take the ContentPanel out of the TabPanel and put it directly into the Viewport scrolling works as expected. Any ideas on why this is happening when using a TabPanel container and if there is any way to fix it for FF?